bluewave

The faster flow is the reason for the strong storm tracks through the lakes instead of relaxing and giving us a quiet ridging pattern.

Not an easy feat with such a fast Pacific flow and storms racing through the Great Lakes.

I agree with this. The much faster Northern Stream of the Pacific Jet since 18-19 is the primary reason that we had such low snowfall from Philly to Boston. Warmer overall winter temperatures and especially the warmer storm tracks. The warmer storm tracks have prevented us from having a snowy winter in a warmer pattern like we often got back during the mid to late 2010s. So we finally got a winter near with near average temperatures this year. But the best we could do is a reversion to the much lower recent 7 year mean for snowfall. So the Pacific overpowered what used to be colder and snowier teleconnections as recently as last decade. Reversion to the 7 year snowfall mean in 2025 from Philly to Boston Monthly Total Snowfall for Philadelphia Area, PA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Mean T 0.5 1.0 4.4 4.0 0.6 0.0 10.5 2024-2025 0.0 T 0.3 4.6 3.2 0.0 M 8.1 2023-2024 0.0 T T 8.0 3.2 0.0 0.0 11.2 2022-2023 T 0.0 T T 0.3 T 0.0 0.3 2021-2022 0.0 0.0 T 12.1 0.4 0.4 0.0 12.9 2020-2021 0.0 0.0 6.6 3.0 14.3 0.0 0.0 23.9 2019-2020 0.0 T 0.1 0.2 T 0.0 0.0 0.3 2018-2019 0.0 3.6 0.3 2.6 6.6 4.0 0.0 17.1 Monthly Total Snowfall for New York-Central Park Area, NY (ThreadEx) Click column heading to sort ascending, click again to sort descending. Mean 0.0 0.9 2.3 3.7 6.4 1.6 T 14.9 2024-2025 0.0 0.0 2.8 3.0 7.1 0.0 M 12.9 2023-2024 0.0 T T 2.3 5.2 T 0.0 7.5 2022-2023 0.0 0.0 T T 2.2 0.1 0.0 2.3 2021-2022 0.0 T 0.2 15.3 2.0 0.4 0.0 17.9 2020-2021 0.0 0.0 10.5 2.1 26.0 T 0.0 38.6 2019-2020 0.0 0.0 2.5 2.3 T T T 4.8 2018-2019 0.0 6.4 T 1.1 2.6 10.4 0.0 20.5 Monthly Total Snowfall for Boston Area, MA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Mean 0.6 0.0 4.6 10.2 8.7 2.4 0.2 26.6 2024-2025 0.0 0.0 5.7 8.2 14.2 0.0 M 28.1 2023-2024 0.0 T 0.2 9.0 0.5 T 0.1 9.8 2022-2023 0.0 T 1.0 6.9 3.6 0.9 0.0 12.4 2021-2022 0.0 T 0.4 36.2 15.3 2.1 T 54.0 2020-2021 4.3 T 13.0 5.8 15.3 0.1 0.1 38.6 2019-2020 0.0 T 11.5 3.1 0.5 T 0.7 15.8 2018-2019 0.0 0.1 0.1 2.1 11.6 13.5 T 27.4

No snow is the new normal for March in the 2020s. Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Mean 0.1 0.1 2025 0.0 0.0 2024 T T 2023 0.1 0.1 2022 0.4 0.4 2021 T T 2020 T T

But January 2021 was our most negative NAO winter month of the 2020s so far both at 500 mb and the surface. And it was still a mild January in the Northeast. Caribou finished at +7.9 and had their 10th warmest January on record. So such a strong -NAO in an earlier era in January was much colder in the Northeast even if there was also a trough near the Pacific NW.

We had a big divergence between the CPC PNA and the 500 mb PNA especially in February which had the classic 500 mb -PNA vortex in the PACNW even though CPC index was +PNA. I liked your old idea of creating custom 500mb indices. I think the divergence between the AO and NAO is less if we just used the 500 mb composites and didn’t use the CPC. My guess is the 500 mb NAO would be negative more often than we have been getting from the CPC. So the NAO and AO would align more at the 500 mb level.

The specific phenomenon are strongly influenced by the global temperatures at any given time. This is why teleconnections which were cold in the 70s to early 90s haven’t been as cold anymore. Plus the coldest recent month in the Northeast was during one of the strongest +NAO winters on record in February 2015. January 2021 was the most negative 2020s winter NAO month and it was mild in the Northeast. So other teleconnections and patterns have a much bigger influence than the NAO in the Northeast.

The state of the NAO whether positive or negative doesn’t cause the Northern Hemisphere cold pool to get smaller like we have been seeing resulting in the limited area of these Arctic outbreaks.

Montana has been one of the small areas in North America with 4 top 10 coldest Februaries since 2018. So these Arctic outbreaks have been focusing in smaller geographic regions. In the old days the cold dropping down the Plains would spread out to the East Coast. Now the core of the cold stays in a narrower corridor closer to the Plains and Midwest. Time Series Summary for Great Falls Area, MT (ThreadEx) - Month of Feb Click column heading to sort ascending, click again to sort descending top 10 coldest Februaries since 1892 1 1936 -5.2 0 2 2019 -0.2 0 3 1922 9.0 0 4 1989 10.3 0 5 1899 11.0 0 6 2025 11.3 0 7 2018 11.8 0 8 2021 12.4 0 9 1975 13.1 0 10 1978 14.4 0

Maybe the higher 500mb heights near the East Coast are influencing the location of the wave breaks which have been leading to the orientation of the -AO and -NAO blocks during the 2020s.

It hasn’t made a difference whether it was a -NAO or -AO during the 2020s. March 2023 was one of the most negative NAO months of the 2020s so far. We still got the Southeast Ridge link up which forced the storm on the 13 to 15th too far north for my area. So it turned into an higher elevation special. 2023 1.25 0.92 -1.11

There are probably multiple factors contributing to the more +NAO winter trend and -NAO summer trend.

That’s the point. Even when we had strong -PNA -AOs in recent years, the actual 500 mb heights weren’t as low near the Pacific NW as there were in the 1950s to 1970s. So deeper troughs digging into the West during that colder era didn’t pump the Southeast Ridge. During the 2020s all it takes are relatively weak lows coming into the West and we get a big 500mb ridge amplification in the East.

Back in the 50s to early 70s we seldom had a Southeast Ridge when there was a strong -PNA -AO pattern. So the Southeast Ridge becoming such a big player in our sensible weather is a more recent phenomenon. My guess is that it’s a function of the much warmer global SST and land temps along with the warming at 500mb.

I think the more +NAO could be a function of the increased KB blocking low sea ice feedback. We used to get a much stronger vortex in Europe when there was such strong blocking across the Arctic in the old days. Instead the KB block build down into Europe preventing the usual cold trough development. So this is also contributing to the Southeast Ridge which has been increasing over the years. But even past instances of a very deep vortex centered south of Greenland like this year didn’t have as strong of a Southeast Ridge. The vortex out there this month was among the strongest that was observed in the February when compared to the other strong years in the composite. But the Arctic blocking was more intense this February than in the composite.

We have been seeing the -AO decouple from the -NAO. We used to get both falling in tandem more often. Now we get -AO and +NAOs more often.

The overall size of the troughs has been shrinking. So the record cold in spots like Nebraska had smaller geographic footprint than in the past. These strong -EPO +PNA and -AO patterns in the past had much more extensive cold and larger troughs. If we just isolate those features, then this was our warmest winter of the group which included 02-03, 85-86, 76-77, and 62-63. So those were much colder teleconnections in the past when the 500 mb ridges weren’t crowding out the troughs.

On the day of the strong cutter back in mid-February that produced the record snows from Toronto to Montreal it was more about the -AO linking up with the Southeast Ridge than the -AO being too far north. In the old days we would have done fine with the block extending west to Baffin Island. These days with the faster Pacific flow and record Atlantic SSTs we get more of these Southeast Ridge link ups. From the 1950s into early 1970s even when we had strong -PNAs, there would be a trough over the Eastern U.S. and not a ridge when there was a -AO.

I had several friends in the airline business when I lived in Long Beach. The West End had plenty of flight crews renting apartments close to JFK. It’s a really great lifestyle if you really enjoy traveling and seeing the world.

Yes during February 2021. So this is the first time since the late 1960s without a KU blizzard here during either a La Niña or El Niño February with a -5 -AO. We had our blizzard in February 2021 before the -AO peak. The February 2010 multiple blizzards with that -5 -AO had the amazing STJ pattern. Back during the weak El Niño in February 1978 with that -5 -AO we had the greatest 1970s blizzard. Then the famous Lindsey Snowstorm in February 1969 with that -5 - AO.

I can remember living back in Long Beach in the old days when the Concorde would fly over just after 9am every morning heading into JFK. Now that was really loud. But you got used to it in Long Beach and it was pretty cool.

But not when we have had the -AO dip below -5 in the past.

We had a very strong Southeast Ridge this February which pushed the storm track well to the north. This was the first time a -5 -AO linked up with the Southeast Ridge. So another case of the -AO not delivering for coastal sections like we saw in December 2022 and numerous other times this decade.

I know that. But with these further north storm tracks, even places outside the traditional snow belts can do very well. While past -5 -AOs favored DC to Boston, this was another one that linked up with the Southeast Ridge which has become a regular occurrence in the 2020s. So the heaviest snows got pushed up into Canada instead with this much warmer storm track. But the most impressive records continue to be in the favored lake effect zones like we just saw in Gaylord.

The EPS is correcting warmer now closer to St.Patricks Day as the blocking is linking up with the Southeast Ridge. So we are finally shifting into more of a spring pattern. As the cool downs behind the fronts become weaker and the warm ups stronger. New run Old run